nmap is a
port scanning utility created by
fyodor (fyodor@dhs.org) using the
Perl philosophy of
There's More Than One Way To Do It (
TWTOWTDI) .. it compiles/runs fairly easily on most all
*nixes .. and has recently been ported to
Windows NT by
eEye (see:
nmapNT).
features include:
vanilla TCP connect() scanning
TCP SYN (half open) scanning
TCP FIN, Xmas, or NULL (stealth) scanning
TCP ftp proxy (bounce attack) scanning
SYN/FIN scanning using IP fragments (bypasses some packet filters)
TCP ACK and Window scanning
UDP raw ICMP port unreachable scanning
ICMP scanning (ping-sweep)
TCP Ping scanning
direct (non portmapper) RPC scanning
remote OS identification by TCP/IP Fingerprinting
reverse-ident scanning
etc.
http://www.insecure.org/nmap